Salt intake linked to heart disease-related deaths worldwide

Eating too much salt contributes to 2.3 million deaths from heart attack, stroke, and other cardiovascular diseases -- representing 15 percent of all deaths from these causes -- reported researchers from the Global Burden of Diseases Nutrition & Chronic Disease Group at a major American Heart Association epidemiology meeting today.

The researchers analyzed 247 surveys of adult sodium intake and extrapolated how this sodium intake could affect blood pressure, heart disease risk, and premature deaths from heart-related causes. Like a study presented earlier in the week that linked sugar-sweetened drinks to 180,000 global deaths each year, the salt data only shows an association, not a cause-and-effect relationship.

The fact that the association is entirely extrapolated based on heart-related death data is a huge flaw with the analysis, according to Steven Nissen, MD, a cardiologist with the Cleveland Clinic.

"They're trying to extrapolate millions of death based upon salt intake, but it's not based upon any data on mortality and salt," he said. "It's also based on an extrapolation of the effect of sodium on blood pressure, which is a very big reach, and not a reliable estimate of the burdens of salt."

The effect of salt on blood pressure isn't even that well-established, Dr. Nissen said, and even less well-documented is blood pressure's direct effect on mortality. "There's no question that higher sodium intake does slightly raise blood pressure, which is a risk factor for heart disease," he said. "But some studies show only a one millimeter difference in blood pressure in those on a high-sodium versus a low-sodium diet."

Still, Nissen said, it is reasonable to avoid excess sodium intake. "We do know that the DASH Diet, which is low in salt but high in vegetables does appear to lower blood pressure," he said. "There's also very good evidence that controlling blood pressure with medicine prevents stroke and heart attack, but data hyping salt's direct effect on mortality doesn't reflect the reality of this controversy" over sodium and blood pressure.

Three-quarters of the world's population consumes more than twice the daily recommended amount of salt, according to the American Heart Association. Global sodium intake from packaged foods, table salt, and condiments like soy sauce averaged nearly 4,000 mg a day per person in 2010, AHA researchers said, while the U.S. Institute of Medicine recommends consuming only 2,300 mg daily, or less than 1,500 mg if you're over age 51 or at risk for hypertension or other cardiovascular problems.

More than 75 percent of salt intake comes from packaged and restaurant foods and only 11 percent comes from salt added while cooking or eating, according to the U.S. Centers for Disease Control and Prevention.

If you're curious about your intake, take this salt quiz to see if you can identify which foods are likely to add the most sodium to your diet, and how much you really know about salt.